The present invention relates to a device and method for transferring material from one location to another, and in particular to a device for loading a pallet with material from a conveyer and unloading a pallet.
At the end of most production lines, the manufactured good or work piece is often packaged in a box or container. If many produced items are to be shipped to the same location, they are often placed on pallets as a means of standardizing material handling. For the purposes of this disclosure, the term xe2x80x9cpalletizingxe2x80x9d includes placing a shipping container onto a pallet and also placing a manufactured good into a shipping container. xe2x80x9cMaterial to be transferredxe2x80x9d refers to the items to be moved, such as from the end of the production line to the pallet. In addition, once a pallet is loaded and delivered, it must be unloaded. In this disclosure, xe2x80x9cdepalletizingxe2x80x9d includes removing boxes from the pallet or removing material from a shipping container.
Currently, there are three major types of systems used for palletizing goods from an assembly line or conveyer belt: manually assisted, conventional unitizing, and robotic-based. Each system is useful and cost-effective depending on a number of factors, including: the speed of the assembly line, the complexity of the movement required to place the material onto the pallet or into a box, the flexibility and adaptability of the particular system in conforming to different loading or unloading requirements, and the uniformity of the goods to be placed onto the pallet.
In a manually assisted system, humans transfer the material from the conveyer belt and place it on the pallet. While this system is good for a slow moving conveyer belt, it is not practical for more rapid assembly lines, or if the item is particularly awkward or heavy. Further, repetitive movement injuries may be caused by repeated lifting, compounding the already high cost of labor.
Conventional unitizing systems are fully automated and are designed to handle either low or high line rates. In this method, boxes from the production line are collected to form a single layer to be dropped onto the pallet through the use of a stripper plate. Typically, this system is used with a single pallet.
Finally, robotic-based systems come in two varieties: gantry systems and pedestal systems. Both of these systems usually handle multiple line inputs and are able to load more than one pallet at a time. These systems usually include servo motors and other sensors to be able to change, in mid-line production, the box or container size by the use of controller software. In this way, they are considered xe2x80x9cflexible.xe2x80x9d
The gantry robotic-based system offers a low footprint-to-pallet ratio as most of its components ride along a track above the pallets to be stacked, thus creating more space on the workroom floor. In the pedestal robotic-based system, a loading arm typically sits on a pedestal and is capable of loading multiple pallets around it, or service multiple input lines. Both the robotic system and the conventional unitizing system are capable of great accuracy in placement of the boxes on the pallet. A drawback to the robotic-based gantry and pedestal systems is that as the overall production rate increases, at some point the equipment will be forced to move at very high speeds, becoming impractical, costly and possibly dangerous. It should be noted that both the manual and robotic systems can be employed to unload a pallet as well.
Given these choices, a gap exists for a mid-level producer of goods who does not want to invest the large amount of capital for a robotic-based or other automated system, or is producing at a level unsuitable for manual loading. For this mid-level producer, many of the boxes to be palletized will be of the same size and will be placed in the same location on a daily basis. In this case, there is no need for an expensive robotic-based system or automated system that is flexible or adaptable to varying conditions, or has a high-degree of accuracy. What is needed is a relatively inexpensive material handling device which is simple yet automated to avoid or minimize the need for manual labor, and which does not provide costly features that are extraneous.
With the foregoing in mind, there have been attempts to solve the deficiencies of prior palletizing systems. Of particular note, U.S. Pat. No. 3,995,745, issued to Chambers, discloses a unit for transferring an article from one workstation to another. Referring to FIGS. 1 and 2 thereof, and the specification at column 2, the unit includes a radially reciprocating arm for carrying the work piece at its end. Camming means are provided for reciprocating the arm at selected points in a circular sweeping movement. The camming means includes a cam plate having an endless cam track in the form of a groove. A cam follower is received in the cam track. The cam follower is coupled to the arm and thus rotates with the table and is free to move radially with the arm. The cam plate is stationary with respect to the table. Thus, relative movement between the table and cam plate causes the cam follower to progress along the cam track and thereby move the arm radially. The cam track controls the distance and direction of movement of the arm by way of the cam follower. The Chambers patent does not provide, however, a device that is capable of transferring material to more than one location. Chambers is limited to moving goods from one position to another single position. Thus, what Chambers teaches is not useful for addressing the placement of items in a variety of locations, such as what is required for palletizing.
Also of note is U.S. Pat. No. 4,260,319, issued to Motoda et al. The Motoda patent discloses a simple end position control robot, which isolates the position control apparatus from the weight control apparatus, the two being mechanically associated. Although the Motoda patent does not disclose a cam track per se, the two apparatus are controlled in the XY direction by guide rails. U.S. Pat. No. 4,451,196, issued to Harada et al., discloses a transfer apparatus, including a cam follower for transmitting the swing displacements of the driving arms to the driven arms, a hydraulically controlled actuator for moving the arms, and suction cups for securing the work piece for transfer. U.S. Pat. No. 5,085,556, issued to Ohtomi, discloses a simple industrial robot apparatus comprising an extendable arm for palletizing and depalletizing loads onto or from a pallet. The Ohtomi patent also discloses a robot body or frame on which a vertically moveable arm is movably secured.
The above referenced patents do not provide a simple, economical and yet flexible system capable of palletizing and depalletizing material for a mid-level producer of goods. Most notably, the above patents describe robotic-systems that provide a level of flexibility that exceeds the need of such a mid-level producer. Thus, a need persists for further improvements in a material handling device.
In accordance with one aspect of the present invention, there is provided a material handling device which comprises a frame, a plate supported by the frame having at least two cam tracks, a working arm with a first end connected to the frame and a second end remote from the frame, a cam follower coupled to the working arm selectively engageable with each of the at least two cam tracks, a switching element for selectively switching the cam follower into engagement with a selected one of the at least two cam tracks, and an actuator coupled to the working arm for moving the cam follower along the selected one of the two cam tracks, wherein the movement of the cam follower causes movement of the second end of the working arm along a predetermined path corresponding to the selected one of the at least two cam tracks. The cam tracks provided in the plate determine the position of the remote end of the working arm. Thus, once the positions are known where the manufactured items or boxes are to be picked-up or dropped-off, the frame of the material handling device, according to this aspect of the present invention, can be positioned. The cam tracks within the plate are then designed to cause the working arm to travel along a path, determined by the cam tracks, corresponding to the desired loading or unloading points.
In accordance with another aspect of the present invention, the working arm forms part of a pantograph assembly that is coupled to the cam follower. The working arm includes a first member extending from the first end of the working arm and a second member extending from the second end of the working arm. These first and second members are desirably pivotally connected. The pantograph assembly preferably further comprises a first link having a first end pivotally connected to the first member at a position remote from the working arm and a second end pivotally connected to the cam follower. A second link has a first end pivotally connected to the second member at a position remote from the working arm and a second end pivotally connected to the cam follower. The first link desirably is substantially parallel to the second member of the working arm and the second link is substantially parallel to the first member of the working arm. The first and second links are preferably pivotally connected together and to the cam follower. Such pantograph assembly increases the versatility of the material handling device. It allows scaled movement of the working arm so that a relatively small movement of the cam follower along the cam track translates into a larger scaled movement of the working arm. This increases the area in which the material handling device can operate, as it can operate in a wider area without increasing the size of the frame or plate. The present invention takes general advantage of the presumption that most palletizing and de-palletizing will be done with similar sized boxes or manufactured goods over a long period of time without changeover. A further presumption is that there are a limited number of positions in the X-Y plane, parallel to the floor, that a box or item must be placed.
In another aspect of the present invention, the plate is removably supported by the frame and replaceable with plates having different cam track patterns. The removable plate allows replacement plates to be inserted into the material handler allowing different patterns for the working arm to follow. A new plate may be needed if the desired X-Y positioning of the item or box has changed, or if the item or box has changed size. The plates can be changed relatively quickly, thus reducing the down-time of the manufacturing operation. Most preferably, the plate has more than two cam tracks. The plate desirably includes a common area in which the cam tracks communicate. The cam tracks each have a first end communicating with the common area and a second end remote from the common area. The common area is where the cam follower is able to switch from one cam track to another.
In another aspect of the present invention, the switching element comprises a rotary switch plate arranged to engage the cam follower when the cam follower is in the common area. The switching element may also desirably be a linear actuator providing rotary motion. The rotary switch plate may be mechanically driven, electromechanically driven or pneumatically driven.
Preferably, the working arm has a material holder connected to the remote end. The material holder allows the material handling device to grasp and release the material to be transferred. The material holder may comprise a scoop for carrying the material to be transferred. The material holder desirably comprises a vacuum cup for attaching and releasing the material to be transferred. Alternatively, the material holder may include a gripper for grasping and releasing the material to be transferred. The design of the material holder will depend on what the material to be transferred is. If boxes are to be palletized or de-palletized (taken off the pallet), a vacuum cup may be preferred, or a scoop or spatula. However, if a particular manufactured item is to be transferred, a gripper or other grasping device may be desired to pick-up and release the item.
More preferably, the material holder includes a rotary motion actuator for rotating the material holder about a vertical axis of the material to be transferred. The rotary motion actuator may be a linear actuator providing rotary motion or a timing belt connected between a stationary hinge and the material holder. The use of the timing belt maintains the same orientation of the material from the loading to unloading area. A rotary actuator allows the box or item on the material holder to be rotated to a desired orientation for loading or unloading. The material holder desirably comprises a vertical actuator for moving the material holder in a vertical direction. This allows the material holder to grasp and release the material to be transferred at varying heights. Typically, the loading position for the material to be palletized will be on a conveyor belt. Most often, the elevation of the conveyor belt will be different from the stacking height of the pallet. Thus, the material holder preferably is able to adjust for these differences. Further, once a layer has been placed on or removed from the pallet, the stacking height will be different, requiring the material holder to compensate for the new elevation.
Preferably, the material handling device further comprises a programmable controller or a hardwired system for controlling the operation of said material handling device. More preferably, the material handling device further includes a plurality of sensors mounted on the frame and along the predetermined path and the programmable controller receives input information from the plurality of sensors. At least one of the sensors desirably is arranged where the material to be transferred is lifted by the material holder and at least another sensor where the material to be transferred is released by the material holder. As may be required, the programmable controller controls the position and timing of the movement of the actuator, the vertical actuator, the switching element, and/or the rotary motion actuators. The programming feature allows the material handling device to know when and where the material to be transferred is and where it is supposed to end up. A plurality of sensors in intermediate positions along the cam track further defines additional loading or drop off points for the material holder. Also, an embedded controller or microprocessor can be located on the cam track plate containing data on the intermediate positions can be incorporated and read by the controller. The programming feature can determine where to stop the actuators in order to place the working arm in the desired position, as well as control the speed at which the material handling device operates.
In another aspect of the present invention, two or more plates can be connected to the material handling device. The second plate is positioned underneath the first plate and also preferably underneath the actuator as well. The cam follower is able to switch between the plates using a pin actuator. The cam is held in place by a shift slide lock. This added feature allows the user to easily and quickly switch between two patterns of palletizing or de-palletizing by using the pin actuator to switch the cam between the multiple plates. Most preferably, the second plate has more than two cam tracks.
In accordance with another aspect of the present invention, the material handling device comprises a frame; a pantograph track plate supported by the frame and including at least two cam tracks. At least one pantograph assembly is movably connected to the frame and has at least one end receivable within each of the at least two cam tracks. A material holder is also connected to the pantograph assembly with an actuator connected to the material holder. A cam follower is coupled to the pantograph assembly and is receivable within each of the at least two cam tracks for guiding the direction of the material holder during operation. A switching element for switching the cam follower between the cam tracks is also provided. The material holder moves along a path of movement corresponding to the cam track in which the cam follower is positioned. The pantograph assembly increases the operating area of the material handling device. Preferably, the pantograph assembly comprises at least four rigid members pivotably connected to form a parallelogram. More preferably, one of the rigid members is connected to the material holder. One of the rigid members is also desirably connected to the actuator. Relatively small movements of the cam follower along the cam track are translated into relatively large movements by the material holder due to the pantograph assembly. Preferably, the actuator moves the pantograph assembly and thereby moves the cam follower along one of the cam tracks. The actuator is desirably driven by electromechanical means. The actuator may also be driven by hydraulic or pneumatic means.
Preferably, the at least two cam tracks guide the movement of the material holder in a substantially horizontal plane. Also preferably, one of the cam tracks sets predetermined positions for the material holder in a substantially horizontal plane. The pantograph track plate is preferably removably supported by the frame. This provides the ability to easily remove one pantograph track plate and replace it with another plate having a different cam track pattern. The pantograph track plate preferably has more than two cam tracks. The pantograph track plate desirably includes a common area where the at least two cam tracks converge. Each cam track has a first end within the common area and a second end remote from the common area. Preferably, the switching element is a rotary motion actuator. This actuator can be mechanically, electromechanically or pneumatically driven. The switching element is used to move the cam follower within the common area.
The material holder preferably includes a vertical actuator for moving the material holder in the vertical direction. This allows the material holder to grasp and release material to be transferred at varying elevations. Preferably, the material holder comprises a scoop, vacuum cup or gripper depending on the size and shape the material to be transferred. The material holder desirably comprises a rotary motion actuator for orienting the material to be transferred relative to already positioned material. This aids in the alignment and orientation of the material either on the pallet or the box.
The material handling device is preferably operated by a programmable controller. The material handling device preferably also includes a plurality of sensors placed along the cam tracks where the programmable controller receives input from a plurality of sensors. These sensors monitor the position of the cam follower along the cam track and thereby are also monitoring the position of the material holder. Sensors may desirably be laced where the material to be transferred is picked up by the material holder and where the material is to be dropped off. These sensors alert the material handling device to the presence of an item to be transferred and whether the drop off point is clear. As may be required, the programmable controller preferably controls the position and timing of the switching element, the vertical actuator, the rotary motion actuators and/or the horizontal motion actuator. The operation of the material handling device may also be accomplished by using an embedded controller or microprocessor located on the cam track plate. This embedded controller or microprocessor contains information on the shape of the cam tracks and alerts the control system where to stop the cam follower at an intermediate position along the cam track.
A further embodiment of the present invention provides for a method for handling material comprising the step of providing a material handling device comprising a frame; a cam track plate movably supported by the frame, the cam track plate having at least one cam track; a working arm movably connected to the frame and partially received within the at least one cam track; an actuator assembly connected to the frame and the working arm for moving the working arm within the at least one cam track; and a cam follower coupled to the working arm and partially received within the at least one cam track for guiding the working arm within the at least one cam track. The method further comprises the steps of placing a payload to be transferred in a loading position adjacent to the working arm and transferring the payload to be transferred to the working arm. An actuator assembly moves the cam follower along the at least one cam track resulting in the working arm, carrying the material to be transferred, moving to an unloading position. The payload to be transferred is then placed onto the unloading position.
Preferably, a pantograph assembly is connected between the working arm and the cam track plate. The pantograph assembly is movably connected to a stationary point and partially received within at least one cam track. Desirably, the loading position is on a pallet. It is also preferable that the unloading position is on a pallet.
These and other aspects of the present invention will become apparent from a reading of the following disclosure and claims in conjunction with the drawings herein.